Wake on LAN fails

I tried Wake on LAN in Advanced IP Scanner 1.5 and one time it works and the next nothing happens (no wake up).
Everything is set in the BIOS and the packet is send and received (according to Advanced IP Scanner) but it doesn't wake up.

I am tried this in a secure work area and it seems firewall might cause the problem i don't know.

Is there some more information about wich port needs to be open.
Strange though that one time it works and the next nothing happens so you would suggest that the port used is allready open.